C-Arm Field Generating Apparatus For Removing Material From Blood Vessel Walls

ABSTRACT

Systems and methods for removing plaque from blood vessels by applying constant or time varying magnetic or electrical fields. In one embodiment a system includes winding configurations positioned about a central axis along which a body region may be placed. Each winding configuration generates a magnetic field in a direction which passes through the body region. A first winding configuration generates a first magnetic field component perpendicular to a second magnetic field component generated by a second winding configuration. In a related method for removing a deposit of plaque from a position along a wall of a blood vessel a magnetic field is applied which has a net direction predominantly orthogonal to the direction of the flow of blood through the vessel.

PRIORITY BASED ON RELATED APPLICATION AND INCORPORATION BY REFERENCE

This application is filed as a divisional of U.S. application Ser. No.13/982,784 filed in the USPTO on Jul. 31, 2013 issuing on Nov. 28, 2017as U.S. Pat. No. 9,826,996, which was a National Stage applicationclaiming priority to PCT Application No. PCT/US2012/023271 filed Jan.31, 2012, which claimed priority to U.S. Provisional Application No.61/438,198 filed Jan. 31, 2011; this application is also a continuationof U.S. application Ser. No. 14/549,251 filed Nov. 20, 2014, which was acontinuation of U.S. application Ser. No. 13/362,503 filed Jan. 31,2012, which claimed priority to U.S. Provisional Application No.61/438,198 filed Jan. 31, 2011; all above applications and issuedpatents being incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to medical methods and systems and, moreparticularly, to removal of deposits from blood vessels incardio-vascular systems.

BACKGROUND

Peripheral and coronary blockages are caused by deposits of fattysubstances, e.g., cholesterol, cellular waste products, calcium andfibrin (a clotting material in the blood) along the walls of bloodvessels. Combinations of the foregoing are referred to herein generallyas forms of plaque. Conventionally, narrowed blood vessels are widenedor reopened by mechanical means such as angioplasty or atherectomy.These are invasive procedures. With atherectomy plaque is actuallyremoved to enable less impeded blood flow. Atherectomy may be effectedwith a catheter system comprising a cutter blade for separation of thedeposits, a system for dispersing the cut material, and an imagingsystem to guide catheter movement or aid in the cutting process.Generally, angioplasty and atherectomy are costly and complex procedureswhich create potential risks to the welfare of the patient. Moreover,the effectiveness of such procedures is limited, e.g., for treatment ofcoronary disease or blood vessels in the extremities. Nonetheless,because the build-up of deposits along the inner linings of vascularcavities causes life threatening medical problems, the benefits of usingthese methods are often seen to outweigh the risks. Yet, it remainsdesirable to provide a completely non-invasive technique which iseffective, economical and without potential risk to the welfare of thepatient.

BRIEF SUMMARY OF THE INVENTION

According to one series of embodiments there is provided a method forremoving a deposit of plaque from a position along a wall of a bloodvessel through which blood flows in a first direction. The methodincludes applying a magnetic field having a net direction predominantlyorthogonal to the direction of the flow of blood through the vessel. Inone implementation, a treatment method is provided where blood flows ina first direction through the blood vessel of a patient and the firstdirection may be orthogonal to an axis along which the patient ispositioned for treatment. A magnetic field is applied which has a netfield direction based on contributions from a plurality of componentswhose individual field strengths are variable so that the net fielddirection is selectable, i.e., not limited to a direction orthogonal tothe axis along which the patient is positioned. This enables selectionof a net field direction parallel with the axis along which the patientis positioned and selection of a net field direction predominantlyorthogonal to the axis along which the patient is positioned. Treatmentcan thereby include provision of a magnetic field which is in a planeorthogonal to the direction of the flow of blood through the vessel.

A method for removing molecules in a layer of plaque from a positionalong a wall of a blood vessel through which blood flows in a firstdirection includes applying a magnetic field having a net directionpredominantly orthogonal to the direction of the flow of blood throughthe vessel, the field being of sufficient strength to cause dissociationof a first molecule in the layer of plaque from another molecule in thelayer, or from a molecule which forms the blood vessel wall, by severinga bond which otherwise stabilizes the position of the first moleculewithin the layer of plaque. In one implementation a treatment method isprovided for removing molecules in a layer of plaque from a positionalong a wall of a blood vessel through which blood flows in a firstdirection through the blood vessel of a patient. The first direction maybe orthogonal to an axis along which the patient is positioned fortreatment. A magnetic field is applied which has a net field directionwhich is continuously variable and not limited to a directionpredominantly determined by an axial field component parallel to theaxis along which the patient is positioned. Accordingly, treatment caninclude selection of one or more magnetic field directions predominantlyorthogonal to the direction of the flow of blood through the vessel. Thefield is of sufficient strength to cause dissociation of a firstmolecule in the layer of plaque from another molecule in the layer, orfrom a molecule which forms the blood vessel wall, by severing a bondwhich otherwise stabilizes the position of the first molecule within thelayer of plaque.

There is also provided a method for removing molecules in a layer ofplaque positioned along a wall of a blood vessel through which bloodflows in a first direction. A magnetic field is applied which includes acomponent having a direction predominantly orthogonal to the directionof the flow of blood through the vessel. The field generates a Lorentzforce, in response to which charge separation of conductive carriers inthe blood results in an electric field which balances the Lorentz force.In one implementation of the method an orientation of a portion of theblood vessel under treatment is determined. Based on the determinedorientation, a magnetic field is applied which includes a componenthaving a direction predominantly orthogonal to the direction of the flowof blood through the vessel.

A system is provided for removing plaque from a blood vessel. The systemincludes a plurality of winding configurations each positioned about acentral axis along which a body region of a patient may be placed. Eachwinding configuration is designed to generate a magnetic field in adirection which passes through the body region. A first of the windingconfigurations is capable of generating a first magnetic field componentperpendicular to a second magnetic field component generated by thesecond winding configuration.

According to another series of embodiments, a system is provided forremoving plaque from a blood vessel. The system includes first andsecond components which generate a field and a C-arm configured tosupport the components in spaced apart relation while a patient isdisposed between the components and along a first axis. A chassissupports the C-arm and the C-arm is moveable about the axis to rotatethe components about the first axis.

In another method according to the invention molecules are removed in alayer of plaque from a position along a wall of a blood vessel throughwhich blood flows in a first direction. An electric field is appliedwhich has a net direction predominantly orthogonal to the direction ofthe flow of blood through the vessel. The field is of sufficientstrength to dissociate a first molecule in the layer of plaque fromanother molecule in the layer, or from a molecule which forms the bloodvessel wall, by severing a bond which otherwise stabilizes the positionof the first molecule within the layer of plaque.

In still another method molecules are removed from in a layer of plaquepositioned along a wall of a blood vessel through which blood flows in afirst direction. An electric field is applied which has a componenthaving a direction predominantly orthogonal to the direction of the flowof blood through the vessel, in response to which charge separation ofconductive carriers in the blood results in an electric field.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a partial perspective view of a blood vessel of a patientunder treatment, illustrating a magnetic field and an electric fieldvector relative to a direction of a flow of blood through the vessel;

FIG. 1B is a view in cross section taken through a central axis of theblood vessel shown in FIG. 1A under a condition where plaque is formedcompletely around the vessel;

FIG. 2A illustrates a system for removal of plaque from the blood vesselof FIG. 1 according to a series of embodiments of the invention where anelectric field which passes into or through the blood vessel isgenerated with one or more magnetic coils;

FIG. 2B illustrates a system for removal of plaque from the blood vesselof FIG. 1 according to another series of embodiments of the inventionwhere an electric field which passes into or through the blood vessel isgenerated with field plates between which the field is created;

FIG. 3A illustrates a system for removal of plaque from a blood vesselaccording to another series of embodiments of the invention where anelectric field which passes into or through the blood vessel of FIG. 1is generated with one or more magnetic coils in a limited volume of thepatient's body and which can be translated along and rotated about thebody of the patient;

FIG. 3B illustrates system for removal of plaque from a blood vesselaccording to still another series of embodiments of the invention wherean electric field which passes into or through the blood vessel of FIG.1 is generated with field plates in only a limited volume of thepatient's body;

FIG. 4A is a view in cross section of three pairs of double-helix coilsin a system that allows adjusting a magnetic field vector to point inany direction;

FIG. 4B further illustrates the system of FIG. 4A wherein double helixcoil windings are operable to rotate a magnetic field;

FIG. 5A is a view in cross section of coils in a system according toanother embodiment that allow adjusting a magnetic field vector to pointin any direction; and

FIG. 5B illustrates the system of FIG. 5A according to still anotherembodiment wherein the coils are operable to rotate a magnetic field.

Like reference characters denote like elements throughout the figuresand text.

DETAILED DESCRIPTION OF THE INVENTION

Before describing in detail exemplary systems and methods relating tothe invention, it should be observed that, so as to not obscure thedisclosure with details that will be readily apparent to those skilledin the art, certain conventional elements and steps have been presentedwith lesser detail, while the drawings and the specification describe ingreater detail other elements and steps pertinent to understanding theinvention. Also, the following embodiments are exemplary constructionswhich do not define limits as to structural arrangements or methodsaccording to the invention. The embodiments are permissive rather thanmandatory and are illustrative rather than exhaustive.

The compounds that constitute plaque along the walls of blood vesselsare varied. Non-calcified plaques have been reported as comprising about15 to about 35 percent cholesterol, which is an alcohol having amolecular composition of C₂₇H₄₅OH; and calcified plaques have beenreported as comprising about 10 to about 30 percent cholesterol. Thus, amajor component of plaque build-up in arteries is organic material.

Although the theory is not well established, build-up of plaquematerial, which may comprise a combination of organic and inorganiccompounds, may relate to the presence of large molecular chainconfigurations characteristic of complex organic molecules andcrystallization. Cholesterol molecules are carbon chains withsubstantially no significant electrical polarity or formal charges. Itis believed that bonding of these molecules to each other or to theblood vessel walls is predominantly based on London dispersion forces.These attractive forces result when the electrons in atoms of twoadjacent molecules occupy positions that form temporary dipoles. Thebonds result when the momenta of the atoms or molecules are within avery narrow range. When the momenta are outside of this range, i.e.,being either too small or too large, molecules in the flow do not bindtogether or with molecules which form the surrounding blood vesselwalls. According to the invention, due to stringent requirements thatmomenta be within a limited range in order for the attractive forces toappear, bond formation between the adjacent molecules can be preventedand established bonds can be overcome with application ofelectromagnetic fields. That is, under the influence of a changingelectrical potential, the process of bonding or aggregation of themolecules to form a thick layer of plaque can be hampered and anyalready existing weak bonds which otherwise stabilize a thick layer ofplaque can be overcome thereby allowing the molecules to be carried awayin the flow of blood.

A proposed understanding of this process is based on recognition thatblood is a fluid having conductive constituents, plus other componentssome of which deposit to form plaque. Many of the constituents of bloodare susceptible to magnetic fields. An electric field can be establishedby impressing a magnetic field across flowing blood. See FIG. 1A whichprovides a schematic view of a blood vessel through which a magneticfield is applied in accord with an embodiment of the invention. Themagnetic field is generated in a direction perpendicular to thedirection of the flow of blood and the direction of the resultingelectric field is perpendicular to both the direction of the flow ofblood and the direction of the magnetic field. This result, based on amagneto-hydrodynamic effect occurs because the blood, having a non-zeroconductivity, flows through the magnetic field. Lorentz forces, whichare perpendicular to both the direction of the blood flow and thedirection of the magnetic field, act on the charge carriers in theliquid. Generally, the level of conductivity of the blood is a functionof the concentration of red blood cells and certain electrolytes.

Under the influence of a proposed magnetic field, charge carriers in theflowing blood, resulting from dissociation, are displaced in thedirection of the Lorentz forces. As charge carriers of opposite polaritymigrate in different directions in response to the Lorentz forces, thereis sufficient charge separation to create an electric field thatcounters the Lorentz forces. For a blood vessel having a 1 mm insidediameter, in which there is a blood flow velocity of one cm/sec in thepresence of a magnetic flux density of about 0.1 Tesla, the chargeseparation of conductive carriers in the blood can balance with theLorentz forces. This net charge separation results in amagneto-hydrodynamic voltage across the vessel which is on the order ofa few microvolts. As best understood, the net electric field resultingfrom the Lorentz forces influences the association of the slightly polaror non-polar molecules which have accumulated along the wall of theblood vessel. That is, because these relatively large molecules are heldtogether with a relatively low amount of binding energy, e.g., possiblycaused by London Dispersion Forces, the relatively smallmagneto-hydrodynamic voltage is sufficient to cause dissociation of themolecules which form the plaque.

In one series of embodiments a magnetic system is provided which canprevent or reverse the build-up of plaque in tissue structures.Exemplary magnetic systems may generate pulsed or DC magnetic fields,e.g., ranging from 0.01 Tesla to several Tesla, or, in some embodimentsin a range from less than 0.01 Tesla to more than several Tesla. Thereis also provided a completely non-invasive method for removing plaquefrom blood vessels in the heart and other parts of the human body, e.g.,the brain. FIG. 1A provides a partial cut-away view of an exemplaryblood vessel 2 having deposits of plaque 4 along an interior wall 6thereof. A magnetic field 8 passes through the vessel 2. As furtherillustrated by the view in cross section of the blood vessel 2, shown inFIG. 1B, the magnetic field 8 is substantially perpendicular to thegeneral direction 10 of blood flow. The resulting electric field 12 isperpendicular to both the direction 10 of blood flow and the magneticfield 8. The plaque 4 is shown in FIG. 1A to be predominantly only alongone portion of the interior wall 6. It is to be understood that alongother portions of the blood vessel, such as along the plane throughwhich the view of FIG. 1B is shown, the plaque may cover the entirecircumference of the interior wall 6.

Static or pulsed magnetic fields with flux densities in the desiredrange can be generated based on selection of appropriate coil designsand the level of current passed through the coils. In a magnetic systemaccording to one series of embodiments, the direction of the fieldgenerated by these coils can be aligned as needed with respect to bloodsvessel of interest. A system 20 configured for removal of plaque isshown in FIG. 2A. The system 20 comprises a pair of large Helmholtzcoils 22 that can generate a field which surrounds substantially orentirely the whole body 16 of a patient 18. The Helmholtz coils 22according to this example have a substantially circular shape and areparallel to one another. The coils 22 are symmetrically aligned with oneanother to produce a relatively uniform magnetic field 8 in a directionparallel to a central axis 24 along which the patient is positioned,i.e., in this example the axis 24 is in a direction extending from thehead 26 to the feet 28 of the patient 18, and the axis 24 also passesthrough the center of the circular shape formed by each coil 22.

In other embodiments one or more magnetic coils of arbitrary shape maybe arranged about the patient 18 to generate a magnetic fields inmultiple orthogonal directions in order to assure that a magnetic fieldcan be pointed in a direction which passes through one or more bloodvessels of interest as shown for field 8 of FIG. 1B.

With reference to FIG. 3A, in another embodiment a system 30 comprises asmaller pair of Helmholtz coils 32 aligned in parallel with one anotherin a configuration similar to that shown for the embodiment of FIG. 2.The coils 32 are positioned to produce a desired magnetic field in onlya limited volume of the patient's body 16. In this example the coils 32are positioned about the patient's body to pass the magnetic field 8through coronary blood vessels about the heart, e.g., the left maincoronary artery, in order to remove plaque deposits 4 formed along thevessel walls 6. A feature of this embodiment is the ability to move thecoils 32 of the system 30 along, for example, the axis 24 of thepatient's body, and to rotate the magnetic field 8 around the axis in,for example, a plane which passes through the axis 24, while the fieldpasses through the body 16 of the patient. The system 30 includes anelectromechanical subsystem, details of which are not shown, comprisinga conventional C-arm 34 which supports the magnetic coils 32 in spacedapart relation while a patient is disposed between the coils and along acentral axis 24. The C-arm is moveable along the axis 24 to translatethe coils 32 along a direction parallel to the axis 24. The C-arm isalso moveable about the axis 24 to rotate the coils 32 about the axis24. To effect such movements the C-arm is mounted on a moveable chassis36 which may be displaced along a track (not shown) to provide movementof the coils 32 in directions parallel to the axis 24. The chassis 36also permits rotational movement of the C-arm about the axis 24 in aconventional manner. The subsystem includes conventional motorizedmechanisms (not shown) which provide automated translational androtational movement of the C-arm. Although the coils 32 are illustratedas being relatively small in comparison to the coils 22 of the system 20shown in FIG. 2A, the coils 32 of the system 30 may be relatively largewith the system 30 performing the same afore described function butextending imposition of the magnetic field over a much larger portion ofthe patient's body 16 or over the entire length of the body 16. Withsuch a mechanical arrangement it is possible to select a fieldorientation in any desired direction.

Implementation of the disclosed methods for removing plaque isfacilitated by assuring that the direction of the magnetic field has asignificant component perpendicular to the direction of blood flowthrough the blood vessels being treated. In order to effect removal ofthe plaque in a particular blood vessel in a human body, which vesselcan extend in multiple directions, it is desirable that the system becapable of adjusting the magnetic field direction to provide a net fieldorientation approximately perpendicular to the blood vessel undertreatment. As described for the embodiments of the systems 20 and 30,the direction of the magnetic field can be adjusted by moving the fieldgenerating coils, thereby adjusting the direction of the electric fieldcreated by charge separation.

As an alternative to physically rotating coils or other components toadjust the directions of the magnetic and electric fields, embodimentsaccording to the invention may employ winding configurations whichenable pointing of a magnetic or electric field vector in any directionwithout changing the physical orientation of the system componentsrelative to the patient's body.

An example of a magnetic field winding configuration which generatessuch a rotatable field vector comprises a set of three superimposedcoils or a set of three superimposed pairs of coils. Each coil or coilpair generates a magnetic field perpendicular to the field generated bythe other two coils or coil pairs. One example configuration comprisestwo concentric pairs of double-helix coils positioned along a commonaxis (e.g., the axis 24 of FIGS. 2 and 3) which each generate a dipolefield in a direction transverse to the common axis to the two coils. Athird coil or pair of coils, concentric with the two double helix coilsis used to generate a field in the direction of the common axis. Thesystem thus has the capability of generating three field vectors, eachin one of three orthogonal directions. By adjusting the currents in eachcoil set, a net field vector can be created in any direction. For agiven field direction the magnitude of the field can also be adjusted byadjusting the currents in each of the coils appropriately. The threeorthogonal magnetic field components can also be generated with threepairs of double helix coils, three pairs of saddle coils or three pairsof Helmholtz coils or combinations of these coil types. Moreover,individual ones of the desired field components can be generated with asingle coil. By powering the individual coils or pairs of coilsassociated with each of the three field directions with a separatelyadjustable power supply, the coil currents can be temporally varied togenerate a net field that dynamically changes in magnitude or rotates indirection. That is, by independently changing the current amplitudesand/or the current direction in the coils as a function of time, thefield vector will move accordingly.

By way of example, FIGS. 4 and 5 provide examples in a series ofembodiments where the direction of the magnetic field 8 can be rotatedwithout rotating the spatial orientation of the coil systems whichgenerate the component magnetic fields.

FIG. 4A is a view in cross section of an exemplary system 50 having aconfiguration in which three double helix coil winding sets 52, 54, 56are operable to rotate the magnetic field 8 shown in FIG. 1. As furtherillustrated in the partial view of the system 50 shown in FIG. 4B, thewinding sets 52, 54 and 56 are formed about an aperture 58 in which thepatient 16 is positioned. A central axis 60 of the winding sets 52, 54and 56 is shown to coincide with the central axis 24 of the body 18 whenthe patient is centrally positioned in the aperture 58 as shown in thefigures. As indicated schematically in FIG. 4A, the coil set 52comprises a pair of coils a,a′, the coil set 54 comprises a pair ofcoils b, b′ and the coil set 56 comprises a pair of coils c, c′.

Each of the three coil sets 52, 54, 56 may be separately powered togenerate one of three magnetic field vectors, designated B₅₂, B₅₄ orB₅₆, each pointing in one specific direction. Accordingly, the system 50includes three separate current supply controls: control 52 s for coilset 52; control 54 s for coil set 54; and control 56 s for coil set 56.Each control can control the current level in each coil in the doublehelix pair which it powers.

The direction of the field vector generated by each pair of the doublehelix coils can be made orthogonal to the direction of the field vectorgenerated by each of the other pairs of double helix coils. Bymodulating the relative current input to one or both of the coils ineach coil pair, the magnitude of the magnetic field in each of threeorthogonal directions can be adjusted to provide a desired fieldstrength and net field direction. By superimposing three such fields ofappropriate strengths, each generated by one of the three pairs ofwindings, net magnetic fields of desired strength and direction can begenerated. The resulting field may be static, pulsed or time dependentin magnitude and direction and the field may be rotated as desired. Forexample, with respect to a central axis 10 a, parallel to the direction10 of blood flow in the vessel 2 of the patient body 16, a field ofconstant magnitude may be rotated 360 degrees about the vessel axis toremove the relatively weak bonds which bind individual molecules intothe layer of plaque 4 along the wall 6 of the blood vessel 2.

Exemplary double helix coil designs suitable for this application aredescribed in the following U.S. patent applications which are nowincorporated herein by reference: U.S. Ser. No. 12/133,760 “ConductorAssembly Having An Axial Field In Combination With Quality MainTransverse Field”, filed 5 Jun. 2008; and Ser. No. 12/061,782, “WiringAssembly and Method For Positioning Conductor in a Channel Having a FlatSurface”, filed 3 Apr. 2008. See, also, U.S. Pat. No. 6,921,042 alsoincorporated herein by reference.

The three coil sets of the system 50 surround a volume 62 within theaperture 58, in which the patient 18, or a portion of the body 16 of thepatient, is positioned. The magnetic field 8, resulting fromsuperposition of the magnetic field vectors B₅₂, B₅₄ or B₅₆, extends ina direction which is not necessarily orthogonal to the axis 24, butwhich can be positioned orthogonal to an arbitrary directioncorresponding to the direction 10 of the flow of blood in the vessel 2under treatment to remove the plaque 4. Thus, with reference also toFIG. 1, the system 50 generates a net magnetic field vector orthogonalto the axis 10 a along the portion of any vessel 2 under treatment,i.e., in any arbitrary orientation with respect to the axis 24 and thecentral axis of the coil sets. In this simplified example and in otherembodiments, the field source may be static or time varying, e.g.,sinusoidal or pulsed.

FIG. 5A is a view in cross section of an exemplary system 70 having aconfiguration in which two double helix coil winding sets 52, 54, and asolenoid winding 76 are operable to rotate the magnetic field 8 shown inFIG. 1. As further illustrated in the partial view of the system 70shown in FIG. 5B, the winding sets 52, 54 and the solenoid winding 76are formed about an aperture 68 in which a patient is positioned. Acentral axis 80 of the winding sets 52, 54 and the solenoid winding 66is shown to coincide with the central axis 24 of the body 18 when thepatient is centrally positioned in the aperture 68 as shown in thefigures. As indicated schematically in FIG. 5, the coil set 52 comprisesa pair of coils a,a′, the coil set 54 comprises a pair of coils b, b′and the coil 66 comprises a single solenoid coil.

Each of the two coil sets 52, 54 and the coil 66 may be separatelypowered to generate one of three magnetic field vectors, designated B₅₂,B₅₄ or B₆₆, each pointing in one specific direction. Accordingly, thesystem 50 includes three separate current supply controls: control 52 sfor coil set 52; control 54 s for coil set 54; and control 66 s for thecoil 66. Each control 52 s, 54 s can control the current level in eachcoil in the double helix pair which it powers.

The vectors B₅₂ and B₅₄ are in a plane orthogonal to the axis 80 and thedirection of the field vector generated by each pair of the double helixcoils can be made orthogonal to the direction of the field vectorgenerated by the other pair of double helix coils. The field vector B₆₆is parallel with the axis 80. By modulating the relative current inputto one or both of the coils in each coil set 52, 54 and the solenoidwinding 56, the magnitude of the magnetic field in each of threeorthogonal directions can be adjusted to provide a desired fieldstrength and net field direction. By superimposing three such fields ofappropriate strengths, each generated by one of the coil sets 52, 54 orthe winding 56, net magnetic fields of desired strength and directioncan be generated in the aperture 68. The resulting field may be static,pulsed or time dependent in magnitude and direction and the field may berotated as desired. For example, with respect to a central axis 10 a,parallel to the direction 10 of blood flow in the vessel 2 of thepatient body 16, a field of constant magnitude may be rotated 360degrees about the vessel axis to lyse the relatively weak bonds whichform a layer of plaque 4 along the wall 6 of the blood vessel 2.

The three coil sets of the system 50 surround a volume 72 in which thepatient 18, or a portion of the body 16 of the patient, is positioned.The magnetic field 8, resulting from superposition of the magnetic fieldvectors B₅₂, B₅₄ or B₅₆, extends in a direction which is not necessarilyorthogonal to the axis 24, but which can be positioned orthogonal to anarbitrary direction corresponding to the direction 10 of the flow ofblood in any vessel 2 under treatment to remove the plaque 4. Thus thesystem 50 generates a net magnetic field vector orthogonal to the axis10 a along the portion of any vessel 2 under treatment, i.e., in anyarbitrary orientation with respect to the axis 24 and the central axisof the coil sets. In this simplified example and in other embodiments,the field source may be static, or time varying, e.g., sinusoidal orpulsed.

With regard to the several magnetic coil configurations which have beenillustrated, it is noted that numerous other configurations can beassembled. For example, in lieu of the arrangement shown in FIGS. 2A and3A, multiple pairs of Helmholtz coils can be assembled where each pairdirects a magnetic field in a different direction about a region of apatient's body. Also, to effect generation of a magnetic field similarto that shown in FIG. 2A or FIG. 3A, the Helmholtz coil pair may bereplaced with a single coil which may exhibit a less uniform fieldpattern but which nonetheless generates a field having a significantcomponent orthogonal to the direction of blood flow within the vessel 2.That is, each of three component field vectors (e.g., similar to thecomponent vectors B₅₂, B₅₄ and B₅₆) can each be generated with a singlecoil. Also, arrangements of two or three coils can be assembled in lieuof multiple pairs of Helmholtz coils to generate multiple magnetic fieldcomponents, each in a different direction about a region of thepatient's body. A gradient in the field, resulting from generating thecomponents with single coils, may be advantageous. As one example, for ablood vessel which exhibits significant curvature, a somewhatnon-uniform field may improve the ability to simultaneously providemagnetic field components, each of which can be orthogonal to adifferent direction of blood flow at each of two or more positions inthe blood vessel.

Another series of embodiments according to the invention is based onrecognition that the electric field, which facilitates severing of bondsbetween molecules in a layer of plaque, may be established withoutrequiring generation of a magnetic field. While in some applications itmay be advantageous to generate the electric field based on use ofmagnetic coils to create a Lorentz force, in other instances, in lieu ofgenerating the magnetic field 8, an electric field can otherwiseestablished across a blood vessel, e.g., in a direction orthogonal tothe direction of blood flow. For example, a similar or identical resultcan be had by forming an electric potential across the blood vessel 2with, for example, a pair of parallel plates. The field may be static ortime varying, e.g., sinusoidal or pulsed. An advantage of generating theelectric field without a magnetic field is that this can avoid creationof eddy currents which may be undesirable in, for example, tissue of thebrain.

In this regard, FIG. 2B illustrates a system 20 a having an arrangementanalogous to the Helmholtz coil arrangement of FIG. 2A wherein theHelmholtz coils 22 are replaced with a pair of parallel plates 22 a. Avoltage may be applied across the plates 22 a to establish a uniformelectric field 8 a between the plates. FIG. 3B illustrates a system 30 ahaving an arrangement analogous to the configuration of FIG. 3A wherein,in lieu of incorporating the smaller pair of Helmholtz coils 32, thesystem 30 a comprises relatively small parallel plates 32 a aligned inparallel with one another in a configuration similar to that shown forthe coils 32 of FIG. 2A, but with the coils 32 a positioned to produce adesired electric field 8 a in only a limited volume of the patient'sbody 16. In this example the plates 32 a are positioned about thepatient's body to pass the electric field 8 a through blood vesselsabout the heart in order to remove plaque deposits 4 formed along thevessel wall 6. A feature of this embodiment is the ability to displacethe plates 32 a of the system 30 a (e.g., along the axis 24 of thepatient's body 16), and to rotate the electric field 8 a around the axis24 (e.g., in a plane which passes through the axis 24) while theelectric field passes through the body 16 of the patient 18. The system30 a includes an electromechanical subsystem, details of which are notshown, similar or identical to that of the system 30, comprising aconventional C-arm 34 which translates the plates 32 along a directionparallel to the axis 24 and also rotates the plates 32 a about the axis34. The C-arm is mounted on a moveable chassis 36 which may be displacedalong a track (not shown) to provide the movement in directions parallelto the axis 24. The chassis 36 also permits rotational movement of theC-arm about the axis 24 in a conventional manner. Conventional motorizedmechanisms (not shown) provide for automated translational androtational movement of the C-arm.

Although the plates 32 a are illustrated as being relatively small incomparison to the plates 22 a of FIG. 2B, the plates 32 a of the system30 a may be relatively large with the system 30 a performing the sameaforedescribed function but extending imposition of the electric fieldover a much larger portion of the patient's body 16 or over the entirelength of the body 16. With such a mechanical arrangement it is possibleto select a field orientation in any desired direction.

The concepts disclosed for removal of plaque can be applied to specificblood vessels or segments of a blood vessel based on a determination ofblood vessel orientation. For example, recognizing that blood vesselsfollow paths in many directions, orientation of a segment of a bloodvessel under treatment can first be determined by conventional meanssuch as use of two dimensional or three dimensional radiographytechniques, including the techniques used for angioplasty oratherectomy. Accordingly, when applying the disclosed concepts to removeplaque from a segment of a specific blood vessel (e.g., a segment of acoronary blood vessel), an orientation of the segment is established todetermine the direction of blood flow. Then, based on the determinedorientation, a magnetic field is applied which includes a componenthaving a direction predominantly orthogonal to the direction of the flowof blood through the vessel segment, the field generating a Lorentzforce, in response to which charge separation of conductive carriers inthe blood results in an electric field which balances the Lorentz force.Similarly, when applying the concepts with application of an electricfield, e.g., with parallel plates such as shown in FIGS. 2B and 3B, thevessel orientation is first determined in order to orient the electricfield in a direction which is orthogonal to the direction of the flow ofblood through the segment of the vessel. More generally, when applyingthe concepts to treat blood vessels of multiple orientations, one maysequentially rotate the magnetic or electric fields to assure that thedirection of the applied field is made orthogonal to the direction ofblood flow in vessels of different orientations. In embodiments wherethe orientation of each vessel segment of interest is not firstdetermined. The treatment procedure may include a field rotation througha large number of directions to assure that during the rotation eachvessel segment of interest receives a field orthogonal to the directionof the flow of blood therethrough. In some arrangements field componentsmay be established in three orthogonal directions about a limited regionof interest or about the entire body of the patient with recognitionthat provision of field components of sufficient strength there is noneed to predetermine the orientation of the vessel.

A feature of embodiments of the afore described treatment methods isthat while the direction of blood flow through a vessel of interest maybe orthogonal to an axis along which the patient is positioned fortreatment, a magnetic field is applied which has a net field directionis variable and not limited to a direction predominantly determined byan axial field component parallel to the axis along which the patient ispositioned. This feature is distinguished from what is achievable withprior art coil designs where the magnetic fields generated primarilyexhibit axial field components, e.g., such as created with solenoidalwindings along the direction in which a patient is positioned. That is,field configurations according to the invention depart from thosegenerated in systems designed to generate a predominant or invariableaxial field along the direction in which the patient is positioned,e.g., along the central axis 24. Thus treatment can include selection ofa magnetic field direction which is predominantly orthogonal to thedirection of the flow of blood through a vessel of interest. Theorthogonal field is of sufficient strength to cause dissociation of afirst molecule in the layer of plaque from another molecule in thelayer, or from a molecule which forms the blood vessel wall, by severinga bond which otherwise stabilizes the position of the first moleculewithin the layer of plaque.

Also in accord with embodiments of the invention, a treatment method hasbeen described which is not dependent on mechanical movement of fieldgenerating components in order to vary the net field direction.Recognizing that in removing a deposit of plaque from a position along awall of a blood vessel in a patient through which blood flows in a firstdirection, the first direction may be orthogonal to an axis along whichthe patient is positioned for treatment, e.g., the axis 24, butaccording to embodiments of the invention the net direction of theapplied magnetic field may be based on contributions from a plurality ofcomponents (e.g., two or three coils or coil sets) whose individualfield strengths are variable. Consequently, the net field direction isselectable and not limited to a direction orthogonal to the axis alongwhich the patient is positioned (e.g., the axis 24), this enabling botha selection of a net field direction parallel with the axis along whichthe patient is positioned and selection of a net field directionorthogonal to the axis along which the patient is positioned.

Consequently it can be assured that treatment can include provision of amagnetic field which is orthogonal to an arbitrary direction of flow ofblood through a vessel of interest.

Although specific coil designs and plate geometries and methods havebeen illustrated for implementing concepts according to the invention,numerous other designs, geometries and methods are contemplated. Forexample, it is possible to provide rotating field configurations withone or more coils in configurations other than those of a double helixdesign, e.g., with a series of saddle coils or, as noted, with rotatingHelmholtz coils. Further, although embodiments refer to arrangementswhere the fields are translated or displaced, it is also contemplatedthat the body of the patient under treatment may be moved along thedirection of the axis 24 or rotated, e.g., in a plane, and that axialtranslation and rotation may be effected by combinations of movement ofthe fields and the patient.

The disclosed concepts and the invention as claimed are not limited toany particular theory. Further, there is no basis to conclude that theeffects responsible for the prevention and removal of plaque from bloodvessels will become inactive immediately upon removal of a magnetic orelectric field. Rather, the effects responsible for the prevention andremoval of plaque from blood vessels may be active for a significantperiod of time after the time at which the actual presence of theapplied magnetic or electrical fields ceases. Part of this extendedduration may be attributable to a weakening of the bonds betweenmolecules of the accumulated plaque such that the plaque slowlyassimilates into the blood stream.

While the invention has been described with reference to particularembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention.

What is claimed is:
 1. A system for removing plaque from a blood vessel,comprising: first and second components which generate a field; a C-armconfigured to support the components in spaced apart relation while apatient is disposed between the components and along a first axis; and achassis supporting the C-arm, wherein the C-arm is moveable about theaxis to rotate the components about the first axis.
 2. The system ofclaim 1 wherein the components are coils operable to generate a magneticfield in a direction perpendicular to the first axis.
 3. The system ofclaim 1 wherein the components are plates operable to generate anelectric field in a direction perpendicular to the first axis.
 4. Thesystem of claim 1 wherein the C-arm is mounted on a moveable chassis toprovide movement of the components in directions parallel to the firstaxis.